Manufacture of fiber products



Patented Feb. 18, 1936 UNITED STATES! PATENT) OFFICE;

No Drawing. Application October 31, 1930; Serial No. 492,622. Renewed August 11, 1934 2 Claims. (01. 92-20) a '-My invention relates to the manufacture of fiber products' by water-processing, as it may be called, my object being to improve and cheapentthe process of manufacture, and also the produo In making paper and fiber board, very large quantities of water are generally used to prepare the pulp suspension and facilitate the formation of the desired sheet or article from the pulp,- whether on wires or in a mold. In forming the fiber article, most of this water is drawn or drained ofi from the fibers, leaving them interlaced in a moist aggregate whose water content (for sheets from which fiber board is to be made) may. approximate by weight. Most of the water thus removedknown in the trade as white wateris filtered after use and allowed to go to waste; i..e., only a small proportion of the white water is ever used a second time.

This wasting of white water is unobjectionableand even, on the whole, advantageousfor mills that have ample supplies of fresh water and can disposed of their white water without ob-jectionably polluting rivers or streams. On the .other hand, a great many mills are restricted as regards water supply or opportunity for waste disposal,-or both,so that it would be desirable for them to reuse their white water as often as possible. Repeated use of thesame water, however, would be objectionable; because the water would become slimy and even maloderous, and contaminated by decomposition of fine fiber particles therein. Hence the fiber products made with such water would. be inoculated at the outset with the very organisms that tend to cause decay of the fibers.

Attempts to cut down the requirements for fresh water and reduce pollution difliculties by purifying or regenerating white water, as by the use of coagulants like alum to eliminate of remove slime, have met with very indifferent success, in part because of the large sedimentation tanks that would be required to permit removal of the coagulated slime.

My present invention not only makes it possible to reuse white water indefinitely in waterprocessing fiber stock into formed fiber products,

but reduces the requirements for fresh water to the very minimum: i. e., it permits the use of a closed or balanced white water system, in which the initial supply only needs periodic replenishment to make up for the water retained and removed in the formed fiber product-since the evaporation losses are inconsiderable. Thus the consumption of water in preparing each batch of pulp is met or balanced by recovery of water drained away in forming the product, so that operations are continued indefinitely with the original body of water, plus only the small compensatory -make up" of fresh water in each batch.

This is the direct antithesis of ordinary practice, in which all the white water is wasted. It

is also an important advance over previous efforts to regenerate and reuse white water (with the aid of coagulants, etc.) where large amounts of the regenerated white water were run to waste, and correspondingly large amounts of fresh water were used in each batch of-- pulp. In referring to whitewater, I do not, of course, mean 'to include the water used in cooking, grinding, refining, washing or otherwise preparing fibers or. fiber stock? (as itis called) which is mixed with white water to form the pulp, whereby dirt is eliminated from the raw fibers, or cooking chemicals are recovered from chemically prepared fibers. Onthe contrary, I refer to the water drained from the sheet or other fiber product in the forming operation. This water does not come in contact with the original dirt attached to the fibers, so that it can be kept comparative-1y clean. a I

In the manufacture. of fiber products accord ing to my invention, a substantially constant body of white water is used, circulating in a closed water-processing cycle, system, or circuit,-as from pulp mixer to sheet forming machine, to drainage tanks, and back to mixer; and so on over and over again, to process portion after portion of fiber stock. This I make possible by adding to the white water a small amount of toxic material which will destroy or render harmless the organisms that produce sliming and decomposition, so as to prevent slime and decomposition of fine fiber and of sizing material. In order to maintain substantial constancy of the amount of white water in the system, I use in each batch of wet fiber stock introduced into the mixer, and there made up with white water into fiber pulp, only just substantially enough water to make up for that which is retained and removed from the system in the formed product: i. e., in general, I reduce the water content of the wet fiber stock batch beyond what is commonly left in it from the wet processes of fiber preparation. This may be done by filtering, deckering, or centrifuging the fiber stock until its moisture content just substantially equals that of the formed product as it is transferred from the forming apparatus to the first stage of the drying operation. In

practice, this means a water content of about 75% by weight, or even less. With each batch of fiber stock, I also add or include an amount of toxic material just substantially equal to that retained in a corresponding amount of the formed product, so as to keep the toxicity of the white water substantially constant.

A great variety of well-known toxic agents or materials can be used, including the many wellknown -toxic metal salts, etc. Amongst watersoluble "agents I may particularly instance sodium fluoride, carbolic acid, zinc chloride, and sodium bichromate; amongst insoluble agents, zinc meta-arsenate, dinitrophenoland chlorinate ed naphthalene. The quantities preferred will depend on the character or quality of the fiber product that is desired, and on the amount'of fine fiber and sizing material that. escapes irom the forming machine into the white water system. In general, very satisfactory results will be obtained with 1% of toxic agent to fiber, or less,-reckoni-ng on a bone-dry basis -in the initial mixer batch, tor a system operating with. about 50,000 lbs. of water in the mixer at each batch. This will toxify the total body of white water to a sufficient degree, so that subsequent batches need only contain enough toxic agent to make up for that removed in each sheet or batch of the product. For example, the initial batch may contain:

Pounds Fiber (bone-dry basis)- -1 r 980 Size (such as soluble rosin size-bone dry basis) W 10 Toxic material (such as indicated above) 10 This will be about right for 50,000 lbs. total water in the mixer at each batch.

It is to be understood, of course, that these proportions may be varied very greatly; in particular, the proportion of toxic agent may be con quite resistant to decay or attack by termites or the like, especially when powerful insoluble agents are employed. Less powerful toxic agents may, of course, have to be used in larger 'proportions to give corresponding biological resistance to the board; and soluble toxic agents may likewise have to be used in larger proportions, by reason of the fact that the major proportion of such agents in a mixer batch remains in the white water draining off from the pulp. Solid, undissolved agents, on the other hand, tend to remain behind the fiber, especially if of a bulky, flocculent character.

. Since a system operating according to my invention requires only a constant minimum .of white water therein, it is only necessary to have a capacity of tanlns in the system to supply the sheet "forming machine and afford sufficient reserve ior practical operation,having regard, of

course, to the pipe capacities and other clearprepare the same for use in the forming machine of the system.

2. An improvement in the reuse of white water in processing wet fiber stock, whose water content exceeds that of the formed fiber product, in a. closed system or cycle, while preventing decomposition or in this closed system by the presence of toxic material therein; which improvement comprises reducing the water content of the wet stock entering the closed system to equal that of the formed-fiber product leaving said closed system, adding the white water to this stock to prepare the same for use in the forming machine of the system, and also continually introducing into the system amounts of toxic material substantially equal to what is retained in i the formed product, thus maintaining the toxicity in the system substantially constant.

DANIEL MANSON SUTHERLAND, JR. 

